The present invention relates to a method for predicting a power curve for a wind turbine, especially to a method for obtaining a power curve adapted for high altitude operation of a wind turbine. Furthermore, the present invention is directed to a control strategy utilizing such power curve and to a wind turbine in which such control strategy is implemented.
Wind turbines capture kinetic energy from the wind and convert it into electrical power. Since wind turbines can be designed as stand-alone or island solutions, they are especially suited to supply electric power to remote areas. For example, such areas may be located in mountainous regions or elevated plains, i.e. at high altitude. Due to their elevated location, wind turbines installed at those sites encounter a lower air density compared to sea level. The lower air density causes significant deviations from the “normal” operation at sea level. In particular, the power curve of the wind turbines is different for operation in high altitude. Since the power curve is used to predict the annual power output of the turbines, the power curve deviation may adversely affect the quality of power output predictions. Also, the power curve is used as a basis for the control strategy implemented in the turbine controller. Accordingly, turbine control will not be optimal if the implemented power curve does not correctly reflect the actual behavior of the turbine.
For the above reasons, a power curve correction for high altitudes was developed which is known to those skilled in the art as the IEC 61400-12 standard for air density normalization. The IEC standard describes a method how the sea level power curve of a pitch-regulated wind turbine can be corrected for lower air density at high-altitude sites. However, it turned out overtime that still the power curves corrected according to standard IEC 61400-12, edition 1998, do not correctly reflect the turbine behavior and, typically, overrate the power production in the partial load operation range of the wind turbine.